No audio playback in VSE but rendered file has audio
To enable the sound in my Video Sequencing Editor, I had to change the system setting for audio device from OpenAL to SDL. Doing this seemed to jar loose the sound so that it would play.  I was even able to change the setting back to OpenAL and the sound continued to be enabled.  Strange, huh?  The sound works fine now.

Go to File> User Preferences> System> Sound: Audio Device.